Beginning at 11:48 p.m. on July 31, 2000, a series of four explosions occurred in the
Willow Creek Mine, an underground coal mine located in Carbon County, Utah. Most
likely, a roof fall in the worked-out area of the D-3 longwall panel gob ignited methane
and other gaseous hydrocarbons. This resulted in the first explosion and fire. Believing
that a roof fall had occurred, personnel remained on the D-3 longwall section to
extinguish a fire near the base of the shields on the headgate side of the longwall face.
Eventually, liquid hydrocarbons became involved in the fire. Conditions worsened in the
face area just prior to the second explosion. Two closely spaced explosions occurred at
approximately 11:55 p.m. A fourth explosion occurred at 12:17 a.m. on August 1, 2000.
Two fatalities occurred as a result of the second and third explosions. The fire provided
the ignition source for these subsequent explosions. A mine rescue and recovery
operation was conducted and all remaining survivors and the deceased were recovered by
4:00a.m. Appendix A is a list of the injured miners. Appendix E contains the accident
data sheets.

The Mine Safety and Health Administration (MSHA) determined that the bleeder
ventilation system did not adequately control the air passing through the worked-out area
of the D-3 Panel. The system did not dilute and render harmless concentrations of
methane and other gaseous hydrocarbons in the worked-out area where potential ignition
sources existed.

The mine surface openings were sealed at approximately 10:30 a.m. on August 1, 2000.
At present, there is no plan to reenter or reopen the mine. Accordingly, this report is
based entirely on witness interviews and records obtained during the investigation.
Should an underground investigation of the accident scene become possible in the future,
an amended report may be issued.

GENERAL INFORMATION

The Willow Creek Mine is located along highway U.S. 191, four miles north of Helper,
Carbon County, Utah. Beginning in 1996, the mine was developed from five drift
openings by the room and pillar mining method into the Castle Gate "D" seam, which
averages 20 feet in thickness. Mining heights ranged from 7 to 11 feet. The seam dips at
8 to 9 degrees toward the north. In 1999, RAG American Coal, Inc., purchased the
property from Cyprus Western Coal Company, and operated the mine as Plateau Mining
Corporation.

The mine had three operating sections which included two continuous miner sections and
a longwall. The continuous miner sections were developing the right side of D Northeast
Mains and the D-4 longwall headgate. Appendix I contains a copy of the mine map.
Continuous miner sections utilized Joy 12CM-12 continuous mining machines, Joy 22SC
and 32SC shuttle cars, and Fletcher CHDR17CH roof bolting machines.

The longwall section face equipment included a Joy 7LS double drum shearer, 142 Joy
2X920-UST shields, and a Joy M70976-9 face conveyor. The D-3 longwall panel was
projected to be approximately 4200 feet long. The longwall face was approximately 815
feet wide. The orientation of this longwall panel was such that the inby headgate corner
was the point of lowest elevation. The longwall section had commenced retreat of the D-3 panel on July 16, fifteen days prior to the accident. The top nine feet of the seam was
being mined. The longwall had retreated approximately 250 feet at the time of the
accident.

Conveyor belt haulage was used from each working section to the surface. Petitions for
modification at the mine enabled two-entry longwall development. One of these petitions
for modification permitted the use of belt entries as additional intake air courses to
ventilate the longwall face during retreat mining. At the time of the accident, however,
air in the longwall section belt entry was being coursed outby and was not being used to
ventilate the longwall face. The longwall belt haulage entry was monitored for carbon
monoxide (CO) by an atmospheric monitoring system (AMS).

The D-3 longwall panel was the third longwall panel mined. On November 25, 1998, an
explosion and fire occurred in the worked-out area on the tailgate side of the D-1
longwall panel, the first longwall panel mined. All miners were evacuated safely and the
mine was subsequently sealed at the surface. Recovery operations continued until
November 15, 1999, when the longwall was recovered from the D-1 panel and the mine
returned to normal operations. The ignition source for the November 25, 1998, event
could not be determined with certainty because roof falls were discovered throughout the
area where the initial event had occurred and this area was not recovered. However, the
investigation concluded that the most likely source of the ignition was falling rock in the
gob causing either a piezoelectric spark or a spark against a metal object (see MSHA
Report of Investigation, Willow Creek Mine Fire, November 25, 1998). The Mine
Accident, Injury, and Illness Report Form 7000-1, filed by the operator, also stated that
the 1998 fire was believed to have been caused by a roof fall in the gob which ignited
hydrocarbons or methane.

After equipment recovery and sealing of the D-1 longwall panel, the D-2 longwall panel
was successfully extracted. A flow-through bleeder system was utilized during
extraction of the D-2 panel, whereas a wrap-around bleeder system had been used for the
D-1 panel. The D-3 longwall panel was also ventilated with a flow-through bleeder
system.

Through the first two quarters of 2000, the operator reported production of 1.1 million
tons. During this period, an average of 227 miners were employed underground and 76
on the surface. Some of these miners were employed as contract employees. The
longwall section produced coal during two 10-hour shifts, 7 days a week. Maintenance
was performed between production shifts. Approximately once each week, a "double-up" day occurred during which twice the normal production personnel were present.
Various non-production related work was conducted by the extra miners available during
this time. The accident occurred during a "double-up" day. On the day of the accident,
the additional personnel on the D-3 longwall section were performing the following
tasks: removing the block stopping in Crosscut 48; retreating material and equipment;
preparing for the construction of a seal in Crosscut 49; performing cleanup and rock
dusting, and other related work.

The mine Non-Fatal Days Lost (NFDL) rate for January through June of 2000 was 7.86
while the industry average was 8.17. For the April through June quarter of 2000, the
mine NFDL was 7.65 and the industry average was 8.60. The last complete regular
inspection (AAA) by MSHA concluded on June 30, 2000. A regular inspection (AAA)
had begun on July 1, 2000, and was in progress at the time of the accident. From January
1 through July 31, 2000, MSHA inspectors were onsite all but 15 days. MSHA
inspectors were not onsite on July 31. Prior to the accident, MSHA inspectors initiated
256 enforcement actions during the year, as detailed on the chart below:

Type Enforcement Action

Number Initiated 1/1/00 through
7/31/00

104(a) non-S&S citation

50

104(a) S&S citation

183

104(b) order

3

104(d)(1) order

6

107(a) order

1

103(k) order

12

314(b) safeguard

1

DESCRIPTION OF ACCIDENT

The afternoon shift on July 31, 2000, started at 3:45 p.m. William Burton and Richard
Callahan were the two afternoon shift supervisors. Burton oversaw the longwall
operations and Callahan was responsible for the development operations.

Ernie Martinez, the regular afternoon shift longwall section foreman, had participated in
mine rescue training on the day shift and did not work the afternoon shift. Burton
assigned Roger McKinnon, continuous mining machine helper, to fill in for Martinez as a
"Spellboss" for the shift. McKinnon was instructed to select three miners from the D-4
development section to perform outby work in the D-3 longwall section. He selected
Charles Whitten, continuous mining machine operator; David Berdan, shuttle car
operator; and Jas Mills, roof bolter helper. The longwall crew consisted of Wesley
Ellner, tailgate shearer operator; Kyle Medley, headgate shearer operator; Tyson Hales,
stageloader operator; Ronnie Gonzales and Shane Stansfield, longwall mechanics; and
Cory Nielsen, propman. At approximately 3:50 p.m., the longwall crew, along with
McKinnon, Whitten, Berdan, and Jas Mills, boarded the mantrip on the surface and
traveled underground to the D-3 section.

Upon arrival on the D-3 section, the longwall face crew traveled inby to the face area.
McKinnon spent about 15 minutes outby with Whitten, Berdan, and Jas Mills discussing
their assignments before traveling to the longwall face. Mining commenced on the
section with Ellner completing the tailgate cutout and then mining toward the headgate
on the initial pass of the shift. During the shift, Ellner was to provide training to Nielsen
on operating the tailgate drum of the shearer and Medley was to provide training to
Ellner on operating the headgate drum.

After the shearer completed the headgate cutout, a wire rope was attached from Shield 1
to the shearer. The wire rope prevented the shield from tipping over when the pressure
against the roof was released as the shield was advanced. This procedure was performed
due to a mechanical problem with the anti-topple ram between Shields 1 and 2. After this
operation was completed, Ellner gave the remote controls for the tailgate drum to Nielsen
and observed Nielsen as he completed the clean-up pass from the headgate back to the
tailgate.

As the shift progressed, Burton traveled into the mine and arrived on the longwall section
at about 5:30 p.m. At approximately 6:00 p.m., McKinnon received a telephone call and
was informed that the AMS indicated elevated levels of CO on the longwall belt.
McKinnon left the face area and traveled on foot outby in the No. 1 belt entry searching
for the source of the CO. He traveled to the box check at the mouth of the section but
found no indication of CO. McKinnon returned to the longwall face at about 8:00 p.m.
Burton advised McKinnon that the elevated CO levels were not associated with the
longwall belt, but were in reference to a hot roller on Belt UG 3, which was repaired by
outby personnel. About the same time, Vernon Marvidikis and Brent Howell, beltmen,
began rock dusting the longwall belt from Crosscut 21 to Crosscut 47.

At approximately 9:00 p.m., Layne Willson, electrician, was instructed to take a wire
rope into the D-3 section to replace one which had broken during an attempt to prevent
Shield 1 from tipping over. Willson met Jas Mills several crosscuts outby and gave him
the wire rope. Jas Mills delivered the wire rope to the face and Willson exited the mine.
Burton had left the section and was outside by 9:30 p.m. where he talked to Henry Mills,
midnight-shift maintenance foreman, and Kerry Hales, mine manager.

Ellner began the third clean-up pass from the headgate to the tailgate at approximately
9:40 p.m. As the shearer approached the tailgate, at 10:14 p.m., a sudden release of
methane into the face area caused the shearer to de-energize. The longwall crew waited
for methane levels to subside. When the methane did not clear readily, a washdown hose
was utilized in an attempt to dissipate the methane, but this was unsuccessful. McKinnon
arrived and instructed Gonzales and Medley to hang a piece of brattice to help sweep out
the methane. It took approximately 42 minutes for the methane to clear. Although
interruptions in production caused by methane were common, this was reportedly the
longest interruption of the shift. Ellner completed the clean-up pass and the cutout at the
tailgate.

Burton entered the mine around 10:45 p.m. and returned to the D-3 section. At Crosscut
47, he met Jas Mills and instructed him to bring a trailer from Crosscut 12 into the
section. Burton went to the face and Jas Mills trammed the scoop outby toward Crosscut
12.

Medley and Ellner were in the process of mining the fourth cutting pass. Near Shield 35,
Ellner gave his controls to Nielsen. McKinnon was at the tailgate with Gonzales washing
down shields and making sure the tailgate panline was pushed to the face and the shields
were advanced. McKinnon remained in the tailgate area until 11:30 p.m., when he began
his preshift examination for the oncoming crew.

Nielsen completed the cutout at the headgate and the clean-up pass along the first eight
shields. Shields 1, 2, and 3 were not advanced. The shearer was moved toward the
headgate in preparation to attach the wire rope from Shield 1 to the shearer. Ellner was at
Shield 8. Burton, Medley, Tyson Hales, and Nielsen were congregated in the headgate
area. Stansfield was outby their location. Gonzales was shoveling at the tailgate and
McKinnon was at mid-face taking an air reading. Whitten and Berdan had installed the
check curtain in Crosscut 48. They were standing in the No. 1 entry at Crosscut 48. Jas
Mills was hooking the trailer to the scoop in the No. 2 entry at Crosscut 12. Marvidikis
was at Crosscut 8 in the No. 1 entry starting his preshift examination.

First Explosion

At 11:48 p.m., a methane explosion occurred on the headgate side of the D-3 gob.
Outside in the mine office, Dean LaCotta, Jr., AMS attendant, observed that the system
was reporting communication failures with many sensors surrounding the D-3 section.
All of the miners on the D-3 section, and those in close proximity to the section, felt the
forces of the explosion, but most miners interpreted the forces to be a result of a major
cave in the gob. The physical effect of the explosion varied for each miner depending
upon their proximity to the origin. Stansfield, probably located near Crosscut 49, was
thrown by the forces and suffered rib injuries. Burton, located at Shield 3, was knocked
down. Medley's hard hat was knocked off. Ellner felt a blast of air traveling from the
headgate toward the tailgate and turned toward the face to shield his eyes from the
suspended dust. When Ellner turned back toward the shield line, he observed sporadic
blue flames in the toes of Shield 8. He shouted "fire" to alert the miners at the headgate.
Medley and Ellner then observed flames at Shield 6.

McKinnon felt the air reverse direction briefly before returning to its normal direction.
Gonzales also noticed an air change and heard a loud noise in the pillared area,
originating from the headgate side of the gob. He called the headgate to inquire about the
event and spoke with Tyson Hales. During their conversation, Tyson Hales became
aware of a fire near the headgate and advised Gonzales of the situation. Gonzales
immediately left the tailgate and traveled toward the headgate. He met McKinnon near
mid-face. Gonzales suggested that they don their self-contained self-rescuers (SCSRs).
McKinnon conducted an air quality test with a handheld detector and informed Gonzales
there was no need for the SCSR. Following this conversation, McKinnon and Gonzales
ran in the panline toward the headgate.

Jas Mills felt a slight overpressure at Crosscut 12. Assuming there had been a roof fall
in the gob, he continued hooking-up the supply trailer and proceeded to take the trailer
inby. Marvidikis felt a sudden burst of air at Crosscut 8 and also believed it was the
result of a roof fall. He continued the preshift examination of the No. 1 entry. The forces
caused Whitten to lose his hard hat and Berdan to be knocked to the mine floor. They
traveled through Crosscut 48 and observed damaged SCSR units, the SCSR cache box,
and other debris scattered in the No. 2 entry. In the face area, firefighting actions had
commenced. Medley, using a washdown hose, and Nielsen, using a fire extinguisher,
attempted to extinguish the fire along the shields. Ellner left the face to obtain additional
fire extinguishers. Burton called outside to report a major roof fall in the gob and a small
fire behind the shields. Burton also ordered evacuation of the continuous miner sections.

McKinnon and Gonzales reached the headgate area. McKinnon attempted to spray water
with a washdown hose but the water would not reach the fire area. Additionally, the
extinguishing agent dispersed by the fire extinguisher was observed suspended and
moving very slowly along the face. Burton called to the surface again, and directed
LaCotta to contact Jerry Dubois, second shift mine foreman. Dubois was instructed to
send firefighting personnel and more fire extinguishers underground. Burton dispatched
Gonzales and McKinnon to retrieve more fire extinguishers. Gonzales returned to the
face and informed Burton that no more extinguishers were available on the section.
Burton instructed Gonzales to bring rock dust to the area in order to fight the fire.
Nielsen and Medley continued spraying water into the gob where the flames were visible.
The fire would disappear when sprayed with water and reappear at other shields. The fire
was migrating along the shield line.

Burton again called out and instructed LaCotta to call the mine rescue team and advise
them that there was a fire at the mine.

Except for Medley and Nielsen, all of the other miners on the section were either
obtaining fire fighting materials or preparing to evacuate the section. Ellner had backed
the mantrip to between Crosscuts 48 and 49 where Stansfield, Gonzales, and Tyson Hales
were located. Burton traveled through Crosscut 49 to the No. 2 entry and shouted that he
needed fire extinguishers. He headed back toward the face. McKinnon picked up a bag
of rockdust and headed toward the face. Whitten grabbed a fire extinguisher from the
mantrip and followed. McKinnon reached the corner of the No. 1 entry, dropped the bag
of rock dust, and turned to head outby to find another bag. Medley, at Shield 15, sensed
that the situation was worsening. He observed that the fire was now burning more
intensely in the gob and could hear the fire roaring behind the shields. Appendix H is a
copy of the mine map detailing the D-3 longwall section showing the location of miners
prior to the second explosion.

Second Explosion

At approximately 11:55 p.m., a second explosion occurred
in the D-3 gob. The forces of the explosion threw Medley to Shield 6, where he
ended up on his hands and knees in a pool of water and burning hydrocarbons.
Nielsen, who was located on the shield line outby Medley, was thrown to Shield 4
and was asphyxiated as a consequence of carbon monoxide poisoning. The forces of
the explosion threw Burton outby in the No. 1 entry and he ended up by the
stageloader near Crosscut 49. McKinnon was thrown into Crosscut 49 facing the
outby rib. He lost his cap lamp. Burton and McKinnon felt intense heat and each
received burns and other injuries. Burton lost consciousness. McKinnon attempted
to don his own personal SCSR. However, he dropped it and was unable to find it.
Whitten was knocked down and thrown back into Crosscut 49 against the outby rib.
He lost his hard hat, but not his cap lamp. Whitten made his way to the No. 2
entry where he saw Berdan.

Berdan was in No. 2 entry near Crosscut 49. Tyson Hales
was nearby. Gonzales, Stansfield, and Ellner were located in the No. 2 entry
close to Crosscut 48. Gonzales heard the explosion, felt slight forces and
observed dust and debris coming out of Crosscut 49 into the No. 2 entry.
Marvidikis, in the belt entry near Crosscut 25, felt a small rush of air and
believed that it was another cave. He continued the preshift examination in the
No. 1 entry, traveling inby.

Gonzales and Stansfield signaled the miners near
Crosscut 49 to evacuate. Ellner was at the driver's door of the mantrip and was
entering the vehicle. Gonzales opened the back door on the driver's side while
Stansfield was preparing to enter the passenger side.

Third Explosion

At approximately 11:56 p.m., a third explosion occurred
in the gob. The forces of the third explosion likely resulted in Stansfield
being fatally injured. Tyson Hales was seriously burned and received a massive
head injury. Ellner was injured when he was thrown into the dashboard of the
mantrip and felt intense heat. Both Whitten and Gonzales were thrown past the
mantrip by the force of the explosion. Berdan was apparently knocked
unconscious. Gonzales, Whitten and Berdan received burns and abrasions from the
explosion. McKinnon, in Crosscut 49, experienced difficulty breathing and passed
out. Medley, on the face near Shield 6, felt debris pelting him. Burton was
located in the No. 1 entry near the stageloader, still unconscious. Marvidikis,
near Crosscut 24, was knocked down and rolled outby in the No. 1 entry about 10
to 15 feet, losing his hard hat. He traveled through a mandoor where he found a
pager and called outside. LaCotta advised him that there was a fire on the face
and that everyone was to evacuate. Jas Mills was between Crosscuts 15 and 20
when the explosion force blew his hard hat off. He observed that the air became
dusty and seemed to reverse. He donned his respirator and waited until he felt
the air begin to flow inby.

Ellner exited the mantrip and traveled outby a few
crosscuts on foot until he came upon Burton's truck. Because Burton's truck was
facing inby, Ellner backed it outby for several crosscuts until he found a
location where he could turn the truck around. He traveled alone toward the
mouth of the section. Although Gonzales had problems breathing and seeing, due
to the dusty conditions, he struggled to his feet and started walking outby.
Gonzales located the six-inch water line in the No. 2 entry and used it as a
guide for traveling out of the section. He heard a back-up alarm from a vehicle
and followed the sound outby for some distance. Whitten found himself along the
rib line. His hard hat, cap lamp, and SCSR were missing. Whitten felt his way
until he saw a faint light, which turned out to be the longwall transformer. He
continued walking out of the section.

Ellner came upon Marvidikis near Crosscut 25, as
Marvidikis was completing his phone call to the surface. Ellner shouted to
Marvidikis that there had been an explosion and that he should get in the truck.
Ellner continued driving outby with Marvidikis. Ellner collided with the scoop
operated by Jas Mills as he attempted to pass. Ellner maneuvered around the
scoop and told Jas Mills to get in the truck. Jas Mills decided to move the
scoop so others coming out of the D-3 section would have clearance to pass the
scoop. Ellner and Marvidikis changed positions in the truck and Marvidikis
drove. As they got near the mouth of the section, they passed Willson and
another miner, who were transporting fire extinguishers to the section. Ellner
and Marvidikis continued to the surface where they arrived at approximately
12:12 a.m.

As Willson traveled inby, he passed Jas Mills and
Gonzales. He came upon Whitten at Crosscut 39 and decided to turn around, pick
up these three injured miners, and transport them to the surface. As they
traveled outby, they met Henry Mills, Boyd Moosman, midnight shift maintenance
foreman, and four other miners heading inby. Willson informed Henry Mills of
their decision to exit the mine. Henry Mills and the others continued to travel
inby. At Crosscut 46 or 47, it became apparent to Henry Mills and Moosman that
there had been an explosion. At that moment, Henry Mills received a signal from
his personal emergency device (PED), indicating that all miners should evacuate.
They drove out, reaching the surface around 12:45 a.m.

The miners that were left on the section began to move
from their locations and interact with each other. Medley, who had donned a
10-minute SCSR, crawled himself from the face to Crosscut 49. He saw a cap lamp
on the mine floor. He felt his way along the cord to Burton, who was beginning
to regain consciousness. Burton crawled toward the No. 2 entry. McKinnon also
regained consciousness. He staggered over and sat next to Burton near the shop
car, which had been blown more than 50 feet to a location outby Crosscut 49 in
the No. 2 entry. Next to McKinnon were several SCSRs that had been scattered by
the explosion. He retrieved two SCSRs and gave one to Burton. They each donned
an SCSR. Berdan staggered to their location from outby. McKinnon gave a third
SCSR to Berdan, but Berdan could not open it. McKinnon also attempted to open
it, but could not because of the injuries to his hands. Medley crawled out of
Crosscut 49 and continued toward the mantrip. Berdan walked to the mantrip.
McKinnon went to start the mantrip and returned to Burton. He was unable to move
Burton to the mantrip and it was decided that Burton should wait for assistance.
Burton attempted to protect himself from additional injuries by positioning
himself under the shop car.

As McKinnon walked to the mantrip, he saw Tyson Hales
lying on the mine floor. McKinnon, due to his injuries, was unable to assist
Tyson Hales. McKinnon, Berdan, and Medley traveled out of the mine. At this
time, Tyson Hales, Burton, Stansfield, and Nielsen were the only miners
remaining underground. McKinnon, Berdan, and Medley arrived on the surface at
approximately 1:30 a.m. Appendix G shows a photograph of the truck used by
McKinnon, Berdan, and Medley.

Fourth Explosion

Fan data indicated that a fourth explosion occurred at
12:17 a.m. Due to their condition and location, the few surviving miners
remaining on the section do not recall this explosion.

RESCUE AND RECOVERY
OPERATION

At approximately 11:53 p.m. on July 31, 2000, LaCotta
received a telephone call from Burton. Burton requested that the company mine
rescue teams be called to fight a fire in the mine. LaCotta secured a listing of
Willow Creek Mine rescue team members and began calling those individuals at
their homes. Willow Creek Mine rescue team members began receiving calls at
approximately midnight and began to arrive onsite minutes later. MSHA personnel
were notified at approximately 12:30 a.m. and began to arrive at the mine site
at approximately 1:15 a.m.

Ray Haigler, mine rescue team captain, was one of the
first to arrive. Mac Cook, mine rescue team trainer, arrived onsite at
approximately 12:15 a.m. At the direction of Steven Rigby, maintenance manager,
Haigler, along with Moosman, went to the mine return portals to monitor gases at
approximately 1:00 a.m. After checking the three return portals, twice each,
they returned to the command center to report their findings. Cook assisted
Rigby with the outside activities as well as reviewing the gas monitoring
results from the mine portals and the AMS system. Rigby assigned the monitoring
duties to another employee and instructed Haigler and Moosman to prepare the
mine rescue team breathing apparatuses. As of approximately 1:30 a.m., all but
two members of the two Willow Creek Mine rescue team members had been contacted
and were onsite.

At approximately 1:30 a.m., McKinnon, Medley, and Berdan
exited the mine in the D-3 section mantrip. They provided information concerning
at least two of the injured miners still underground. A decision was made to
send a mine rescue team to the D-3 longwall section. Cook assembled a six man
team consisting of Haigler, Moosman, Dave Wood, Lee Montoya, Zach Robinson, and
Ken Powell. Cook briefed the team on what he knew of the events that had
occurred in the mine, atmospheric conditions underground, on the location of
injured miners, and on the need to communicate with the command center. The
remaining Willow Creek team members were to remain on the surface as a back-up
team. Several other mine rescue teams, although not officially called to the
site, had arrived at the mine to offer assistance. They had been temporarily
staying in nearby Price, Utah, preparing to compete in a mine rescue contest
that was scheduled to be conducted on August 1.

The six team members entered the mine at approximately
2:00 a.m. They traveled in two vehicles, three team members in each, taking
first aid supplies, fire extinguishers, water, stretchers, breathing
apparatuses, and gas detection instruments. The team maintained communication
with the command center by pager phones as they traveled into the mine.
Conditions appeared normal until they approached Crosscut 43 of the D-3 longwall
section. At that point, the team members began to observe scattered debris, such
as a trash can and a lunch box, in the roadway. They traveled inby to Crosscut
44, which was the location of the longwall starter box. From there, Haigler
called the command center to report their location and the conditions
encountered. The air at that location was clear and was flowing in the proper
direction. Haigler continued inby on foot, followed by the other team members in
the two vehicles. He searched the crosscuts and under debris in the roadway for
the remaining miners. Near Crosscut 45, the team encountered significant signs
of an explosion in the form of soot, metal stopping panels, and larger items of
debris. The team stopped at Crosscut 47, parked one truck in the crosscut,
turned the other truck around, and parked it in the No. 2 entry.

All six team members assembled near the parked truck at
Crosscut 47. They shouldered their breathing apparatuses, gathered a few first
aid kits and stretchers, and proceeded bare-faced inby in the No. 2 entry.
Conditions in the entry were very black and there was much debris strewn
throughout the entire entry. Upon reaching Crosscut 48, the team encountered
Tyson Hales. He was found near the center of the entry and was partially covered
by a twisted metal stopping panel. Haigler examined him for injuries. A
compressed airline, located above Tyson Hales, was open. The noise it created
made communications difficult. After closing the valve, the team heard Burton
calling from an inby location in the No. 2 entry. Haigler, Wood, and Moosman
gathered first aid supplies and traveled inby.

Powell, Robinson, and Montoya remained with Tyson Hales
to stabilize his condition and load him on a stretcher. Robinson proceeded outby
and backed one of the trucks inby to Crosscut 48. Haigler, Wood, and Moosman
found Burton in the No. 2 entry, halfway between Crosscuts 48 and 49 lying
partially under a shop car. Burton was conscious, alert, and was able to
describe his injuries to the team members. He also relayed to the team that he
thought Stansfield was outby his location and that Nielsen was probably still
inby him. They pulled Burton from under the shop car, stabilized his injuries,
and loaded him on a stretcher. Burton was carried outby toward the truck at
Crosscut 48 where Tyson Hales had just been placed onto the truck by Powell and
Montoya.

In order to place Burton onto the truck, it was
necessary to clear more space. The team members began to unload some of their
equipment and while throwing fire extinguishers toward the rib, Moosman
discovered another miner lying against the outby corner of Crosscut 48 in the
No. 2 entry. The miner was identified as Stansfield. He was positioned against a
timber set along the rib and was covered with brattice cloth. Powell determined
that Stansfield had received fatal injuries.

At that time, the team split up. Robinson, Montoya, and
Powell transported the two injured miners outside. Haigler, Moosman, and Wood
proceeded to explore the rest of the section searching for Nielsen. They
traveled from the No. 2 entry through Crosscut 48 into the No. 1 entry. From
there, they traveled inby and encountered two hard hats, one of which was
McKinnon's. They also found McKinnon's cap light at the outby corner of Crosscut
49. They traveled through Crosscut 49 toward the No. 2 entry and back to where
Burton was found. The three members walked back through Crosscut 49 and went
inby toward the longwall face. At the inby corner of Crosscut 49, in the No. 1
entry, the team encountered light smoke and 4.6 to 4.9 percent methane. At that
point, the team members retreated to Crosscut 44 and reported their findings to
the surface at approximately 2:40 a.m.

During this conversation, Haigler informed the command
center that three team members were on their way out with Burton and Tyson
Hales. He reported the conditions of the injured miners and that Stansfield's
body had been located. Haigler also reported the atmospheric conditions found
inby Crosscut 49. Rigby, after consulting with Burggraf, instructed the crew of
three to go under oxygen and travel to the longwall face in search of Nielsen.
The team found Nielsen at Shield 4. An examination of Nielsen revealed that he
had received fatal injuries. Elevated methane concentrations and light smoke
were present on the face; however, there were no visible flames. The team
retreated to the telephone and contacted the command center to report their
findings.

Rigby and Burggraf discussed the reported findings.
Burggraf instructed Haigler to retrieve Nielsen from the face and bring both
victims out of the mine. Haigler informed Burggraf that they would need
additional help to remove Nielsen from the face. Burggraf told Haigler that the
other three team members would return to the section. Haigler, Moosman, and Wood
remained at the location of the telephone until the other three returned.
Robinson and Powell prepared Stansfield for transport while Haigler, Montoya,
Wood, and Moosman went to retrieve Nielsen from the face. While under oxygen,
the team returned to the face to retrieve Nielsen. The four members removed
Nielsen from the face and carried him to the vehicle. Team members called the
command center to inform them that the recovery was complete and that the entire
team was returning to the surface. All remaining miners arrived on the surface
at approximately 4:00 a.m.

Upon reaching the surface, the team assisted placing
Nielsen and Stansfield into ambulances. The ambulances left the mine site at
approximately 4:05 a.m. A debriefing meeting was conducted in the mine office.
Present were the six mine rescue team members, Burggraf, Ramey, Ray, and Frey.
Haigler provided an account of the underground activities of the team. The
meeting was concluded at approximately 5:05 a.m.

INVESTIGATION OF THE
ACCIDENT

MSHA was notified of the accident at approximately 12:30
a.m. on August 1, 2000, and MSHA personnel began arriving at the site by 1:15
a.m. Preliminary information was obtained by MSHA District 9 personnel during
the rescue and recovery operation. On August 1, the Administrator for Coal Mine
Safety and Health directed that an investigation be conducted by a team
consisting of personnel from MSHA Coal Districts 2, 3, 5, and 11, personnel from
Coal Mine Safety and Health Headquarters, personnel from MSHA's Technical
Support Division, and personnel from the Department of Labor's Office of the
Solicitor. MSHA's District Manager from District 5 in Norton, Virginia, was
assigned as the accident investigation team leader.

The investigation team members arrived onsite and began
the investigation on August 2, 2000. Preliminary information, including records,
were obtained from MSHA and the operator. Mine personnel were identified for
interviews. Witness interviews began on August 7, 2000, at the Price, Utah, MSHA
field office. Subsequently, 37 interviews were conducted with personnel working
at the mine who had relevant knowledge. Other contacts were made and information
was obtained from contractors and state and local authorities. All pertinent
records were obtained and reviewed during the course of the investigation.
Appendix C is a list of persons interviewed and Appendix D shows persons
participating in the investigation.

DISCUSSION

Personal Emergency Device

A Personal Emergency Device (PED) system was in use at
the mine. The system permitted text messages to be transmitted to key personnel
underground. Miners provided with the receiving units included management
officials as well as miners working in remote areas such as beltmen, examiners,
and pumpers.

The use of the PED system was instrumental in alerting
miners underground of the need to evacuate.Miners working in active and remote areas of the mine at the time of
the explosion were notified through the use of the PED. These miners all safely
exited the mine.

Self-Contained Self-Rescuers

The mine was operated under an approved SCSR storage
plan. For the longwall section, 60-minute SCSR storage caches of 10 units each
were maintained at both the headgate and tailgate areas. Mantrip vehicles were
equipped with SCSR caches. Also, all miners carried 10-minute personal SCSR
units on their belts. The 10-minute units carried by miners were Ocenco Model
M-20. The 60-minute units stored in caches on the section and in the mantrip
vehicles were Ocenco Model EBA 6.5. Although injured by the second explosion,
Medley used a 10-minute unit in traveling from the longwall face to the No. 2
entry. It is possible that the atmosphere on the longwall face was irrespirable
at this time. Some other miners, including McKinnon and Burton who were in
Crosscut 49 after the third explosion, donned SCSR units.

Geology

Geology in the area surrounding and including the Willow
Creek Mine includes formations prone to substantial methane liberation, as well
as heavy bumps, bounces, outbursts, and liberation of hydrocarbons. Increased
methane liberation sometimes accompanies bumps, bounces, and outbursts.
Underground coal mines in close proximity to the Willow Creek Mine have operated
with varying degrees of success over the past century. Mines have operated in
the Sub 3, D, K, and A seams. The nearby Castle Gate No. 3 and No. 5 Mines, now
closed, were characterized by violent bumps, and outbursts, as well as methane
liberations, which frequently interrupted operations and resulted in
accidents.

The Willow Creek Mine was developed in the D seam, which
is one of nine seams in the 1000-foot thick Blackhawk formation. From the bottom
to the top of the formation, seams are identified as Sub 3, 2, and 1, then A, B,
C, K, D, and E seams. The D seam lies above the K-D interburden which consists
mainly of sandstones and silty mudstones. The roof material above D seam
consists of thin lenticular layers of mudstone, sandstone, and thin coal layers.
A sandstone layer approximately seven feet thick is located 30 to 35 feet above
the seam. The operator's geologist believed that this sandstone would break
after approximately 400 feet of longwall retreat. The geologist had observed the
D-3 gob caved approximately 20 to 40 feet high. The massive Castlegate
Sandstone, approximately 500 feet thick, is located approximately 700 feet above
the D seam. Overlying the Castlegate Sandstone are the Price River Formation,
sandstones and mudstones, and the North Horn/Flagstaff Formation of interbedded
mudstones, sandstones, thin limestones, conglomerates, and coal seams.

The Willow Creek Mine is located on the north end of the
north-plunging axis of the San Rafael Swell Anticline. The mine is in a
transition zone between three structural provinces: the Colorado Plateau, the
Uinta Basin, and the Wasatch Plateau. The strike of the coalbed is east-west
with the dip to the north at 8 to 10 degrees. Local dips of up to 15 degrees
resulted from differential compaction. Overburden depth above the longwall face
ranges from 2,800 to 2,900 feet.

Mine Ventilation

The mine used a blowing ventilation system. The main
mine fan was a Joy M132-79-900 Axivane fan, which operated at
893 revolutions per minute (rpm). A second identical fan was arranged in
parallel with the operating mine fan and was provided as a backup unit. Mine
records indicated the average operating pressure of the main mine fan during the
week preceding the accident was 9.7 inches water gauge (in. w.g.). The last
recorded weekly air measurements, prior to the accident, revealed approximately
850,000 cubic feet per minute (cfm) of intake air being forced into the
mine through the intake shaft. Airflow exhausted the mine through three return
drift openings and the regulated belt drift opening. Intake air also leaked out
of the mine through airlock equipment doors in the fifth drift opening.

At the time of the accident, separate splits of air
ventilated three sections: the D-4 gate entry development, the right side of the
D Northeast Mains development, and the D-3 longwall section. The left side of
the D Northeast Mains development and the Sub Mains development located in the
bleeder entries were not in operation at the time of the accident. These idle
sections were not provided with separate air splits. Permanent stoppings,
overcasts, and undercasts were used to provide the required separation between
the various air courses.

Fan Pressure Recordings

The operating pressure of the main mine fan was recorded
on both a Bristol pressure recorder seven-day fan chart and by an Allen-Bradley
computer system. The fan chart had been changed at approximately 1:00 p.m. on
July 31, 2000. Figure 1 (see Appendix F) shows the seven-day fan chart.
Although the motion of the tracing arm for the main mine fan spanned
approximately 1.5 in. w.g., the average operating pressure remained
relatively consistent. Three distinct pressure spikes were visible; two near
midnight on July 31, 2000, and another shortly after midnight on
August 1, 2000. These pressure spikes were consistent with explosion
forces.

Due to the sampling and recording intervals, the
Allen-Bradley monitoring system did not record the first explosion pressure
spike. The magnitude of the fan pressures recorded by the Allen-Bradley
monitoring system differed from those recorded by the Bristol recorder.
Figure 2 (see Appendix F) shows the Allen-Bradley monitoring system fan
pressure data during the time of the accident. These pressure spikes were
consistent with explosion forces. Decreases following the pressure spikes were
likely the result of damage to underground ventilation controls.

Natural Ventilation and Barometric
Pressures

Natural ventilation pressure (NVP) can affect the
ventilation of mines. The magnitude and direction of NVP is determined by
factors such as barometric pressure, air temperature and humidity, and elevation
differences within the mine. NVP may assist or counter the effects of the mine
fan. Slight fluctuations in fan operating conditions, due to NVP, are common.
Barometric pressure information was obtained from the National Oceanic and
Atmospheric Administration, U. S. Department of Commerce, for Price, Utah,
for the period from July 16 through August 1, 2000. It appears that
NVP did influence the fan operating pressure at the Willow Creek Mine. However,
the effects of NVP do not appear to have been significant enough to contribute
to the cause of the accident.

Changes in barometric pressure can also cause the
expansion and contraction of accumulated gases within unventilated (sealed) and
poorly ventilated areas of mines. The barometric pressure for Price, Utah, for
11:48 p.m. on July 31 was approximately 24.27 inches of mercury. The barometric
pressure had been rising from 8:00 p.m. to 11:00 p.m., and was steady from 11:00
p.m. until the time of the accident. Changes in barometric pressure did not
appear to significantly impact the conditions within the D-3 panel.

Ventilation Plan and Bleeder
System

The ventilation plan in effect at the mine was initially
reviewed and approved by the MSHA District 9 Manager on
March 25, 1999. Six reviews were conducted and other amendments were
approved. An amendment to the ventilation plan addressing longwall retreat
mining in the D-3 longwall section, alternate seals, and other items was
approved on July 7, 2000.

A flow-through bleeder system with multiple bleeder
entries was used to ventilate the gob of the D-3 panel. Multiple ventilation
configurations were approved for ventilation of the D-3 longwall section. The
configuration described in the ventilation plan as "D-3 Longwall Start-up Head
to Tail and Bleeder Ventilation with Tail Gate Intake" was being used at the
time of the accident.

D-3
Ventilation

The ventilation plan required that 100,000 cfm of
air be delivered to the intake of the longwall. This requirement was identified
in the ventilation plan pursuant to Title 30 Code of Federal Regulations (CFR)
Section 75.325(g)(2), and pertained to the minimum ventilating air quantity
where multiple units of diesel-powered equipment were operated on working
sections. The airflow directed onto the D-3 longwall face was required to be
measured in the No. 1 entry between the last open crosscut and the face at
measurement point location (MPL) #2. The required minimum airflow
velocities on the longwall face at Shields 16 and 126 were 400 feet per
minute (fpm) and 300 fpm, respectively. From July 28 through July 31, 2000,
the operator's records of preshift examinations showed face velocities ranging
from 508 fpm to 830 fpm at Shield 16, and from 356 fpm to 703 fpm at Shield 126.
The preshift report called out on July 31on the afternoon shift indicated 66,300
cfm at Shield 16 and 50,760 at Shield 126. The ventilation plan also required
that face ventilation be increased 10 percent over the ventilation
quantities in the approved ventilation plan when hydrocarbons were present. The
operator's records of preshift examinations indicated that hydrocarbons were
present on the D-3 longwall face during most days from July 17 to
July 31, 2000.

Some of the D-3 intake airflow was not directed onto the
longwall face. A portion of the airflow was directed inby the headgate side of
the longwall face in the No. 2 entry toward the bleeder entries. This airflow
was to be measured at MPL #3, just inby the last open crosscut. As shown in
the configuration described in the ventilation plan as "D-3 Longwall Start-up
Head to Tail and Bleeder Ventilation with Tail Gate Intake", intake air could be
coursed through the D-3 belt entry either inby toward the longwall face or outby
from the last open crosscut to a regulator at the front of the headgate panel.
At the time of the accident, the D-3 belt airflow was coursed outby. In this
scenario, the ventilation plan depicted the airflow ventilating the belt entry
as part of the required 100,000 cfm intake airflow to the longwall face.
The ventilation plan permitted replacement of the stopping in the second
crosscut outby the face separating the D-3 intake from the D-3 belt with a
curtain to facilitate belt structure removal.

Inlets to the
Gob

The total airflow entering the gob of the D-3 longwall
panel was to be measured at MPL #1, MPL #2, and MPL #3. The tailgate intake was
to be measured at MPL #1, located in the tailgate entry just outby the
longwall face. The tailgate intake split was directed into the gob from the
tailgate entry. The ventilation plan required a minimum tailgate intake airflow
of 30,000 cfm. All of the airflow directed onto the longwall face, measured
at MPL #2, entered the gob. Some of the airflow at MPL #3 was directed into
the inby setup entry at MPL #4. The regulator at MPL #4 was also identified as
the mixing chamber regulator in the mine record books.

Outlets from the
Gob

All airflow exited the gob through the two regulated
tailgate bleeder connectors. These Nos. 1 and 2 entry tailgate bleeder
connectors were identified in the ventilation plan as MPL #8 and
MPL #7, respectively.

Bleeder
Entries

At least one entry in the set of bleeder entries was
required to be traveled in its entirety. MPLs were specified in the mine
ventilation plan to determine the effectiveness of the system where the air
entered and exited the bleeder entries. Measurements of methane and oxygen
concentrations and air quantities and a test to determine if the air was moving
in the proper direction were required at these MPLs. The ventilation plan also
specified that the required weekly examination include traveling inby the
longwall face in the headgate No. 2 entry and across the bleeder entries.
Bleeder examination point locations were to be located at intervals of 1,000
feet inby the longwall face in the headgate entries. The plan also stated that
the set-up rooms were not required to be traveled.

The portion of the airflow measured at MPL #3 which
was not directed into the gob at MPL #4, entered the bleeder entries through two
regulated headgate bleeder connectors. These D-3 Nos. 1 and 2 entry
headgate bleeder connectors were identified in the ventilation plan as MPL #6
and MPL #5, respectively.

An intake split was directed into the bleeder entries
inby the headgate bleeder connectors. The measured airflow where this split
entered the bleeder airflow was identified in mine record books under the
location "Return #3 Reg. 76 to 77 XC ". As shown in the configuration described
in the ventilation plan as "D-3 Longwall Start-up Head to Tail and Bleeder
Ventilation with Tail Gate Intake", the intake airflow in this split at the
Return #3 Reg. 76 to 77 XC location was not to exceed 10% of the overall
longwall intake.

The bleeder airflow ventilated the seals of the D-2 and
D-1 gobs before it entered the main return from the D Seam Bleeders and the D-1
Tailgate entries. The total airflow exiting from the D Seam Bleeders and the D-1
Tailgate was measured at locations specified in the ventilation plan and shown
in the plan drawing labeled, "Bleeder to Main Return MPL Locations". MPL B1 and
MPL B2 were located between Crosscuts 6 and 7 in the D-1 Tailgate Nos. 1
and 2 entries, respectively. MPL B3 was located between Crosscuts 6 and 7 in the
D Seam Bleeders No. 3 entry.

Atmospheric Monitoring
System (AMS)

The mine had been granted petitions for modification of
30 CFR 75.350 and 75.352 which enabled two-entry development of longwall panels.
The petition for modification of 30 CFR 75.350 and the mine ventilation plan
required the use of diesel discriminating sensors (DDS) for CO and nitric oxide
(NO) in the entries of the two-entry developments. CO/NO sensors were used in
other beltlines in lieu of point-type heat sensors. The ambient CO level
specified in the approved mine ventilation plan was 2 parts per million (ppm).
The DDS action levels for longwall retreat and recovery were 8 ppm for alert and
12 ppm for alarm. The monitoring system had a 180 second delay to reduce
nuisance alerts and alarms. The range of the CO sensors was from 0 to 50
ppm.

The surface AMS attendant could monitor the gas
concentrations at specific locations. A protocol had been established by the
mine operator for methane concentrations at certain locations. The AMS
attendants were instructed to notify the longwall section to stop production if
the methane concentration reached 4 percent at any of the headgate or
tailgate bleeder connectors (MPL #5, MPL #6, MPL #7, or
MPL #8), reached 1.95 percent at MPL B1, or reached
0.9 percent in the longwall tailgate intake. Production could resume when
the methane concentrations at those locations decreased to 3.7 percent,
1.75 percent, and 0.7 percent, respectively. The mine was to be
evacuated and MSHA was to be notified if the methane concentration reached
4.5 percent at any of the headgate or tailgate bleeder connectors
(MPL #5, MPL #6, MPL #7, or MPL #8) or reached
2.5 percent at MPL B1. The longwall section and shift foremen were to
be notified if the methane concentration in the longwall tailgate intake was
1.0 percent or greater.

The AMS data for the period from July 16 through August
1, 2000, indicated that the overall trend of methane concentrations at MPL B1
had been increasing. In the days immediately preceding the accident, the trend
was accelerated. The methane concentration at MPL B1 exceeded the operator's
1.95% action level twice on July 31. The first occurrence was at 2:48 a.m. and
lasted approximately 11 minutes. The second occurrence was at 3:33 a.m. and
lasted approximately 40 minutes. This indicated that the bleeder system was near
its capacity.

Recorded Bleeder System
Airflow Measurements

Two required weekly examinations of the mine had been
completed since the beginning of retreat mining in the D-3 panel. The last
weekly examination was conducted July 25 - 26, 2000. The recorded airflow at
MPL #1 was 49,500 cfm, which was greater than the minimum required.
Air quantities were not included in the record for the MPL #2 location
either week. As shown in the configuration described in the ventilation plan as
"D-3 Longwall Start-up Head to Tail and Bleeder Ventilation with Tail Gate
Intake", the airflow at MPL #3 should be similar to the cumulative airflow at
MPL #4, MPL #5, and MPL #6. However, the air quantity recorded
for MPL #3 (113,000 cfm) was not consistent with the cumulative air
quantities recorded at MPL #4, MPL #5, and MPL #6 (32,900 cfm in total).
Testimony indicated that the measurements recorded for MPL #3 may not have
been taken in the location indicated in the ventilation plan. The air quantity
recorded for MPL #4 was 13,200 cfm. The air quantities recorded for
MPL #5 and MPL #6 were 5,200 cfm and 14,500 cfm,
respectively. The total recorded airflow exiting from the gob at MPL #7 and
MPL #8 was 185,600 cfm (100,400 cfm and 85,200 cfm,
respectively). The recorded airflow exiting from the D-1 Tailgate and the D Seam
Bleeders at MPL B1, MPL B2, and MPL B3 was 331,600 cfm (60,300 cfm,
71,500 cfm and 199,800 cfm, respectively).

The airflow ventilating the D-3 panel decreased
following the last completed weekly examination. The recorded face velocities
measured on the longwall face showed a decreasing trend after July 26,
2000. Decreased face velocities indicated a decrease in the airflow ventilating
the longwall face. Information from the velocity sensors positioned at
MPL #5, MPL #6, MPL #7,and MPL #8 were also reviewed. The
velocity sensor data for MPL #5, MPL #6, and MPL #7 did not
appear to accurately represent the airflow at those locations. Therefore, that
data was not used in determining whether airflow changes occurred at those
locations. Velocity data from MPL #8 appeared accurate and also indicated
that airflow at that location decreased from July 27 through 31, 2000. This
condition commonly occurs after longwall start-up when roof falls first begin to
significantly affect the resistance of airflow paths through a pillared area,
often requiring increased ventilating pressure across the gob in order to
maintain adequate ventilation. In such cases, adjustments to the bleeder system
are often required at numerous locations in order to maintain control over
airflow distribution within the worked-out area. Statements revealed that the
regulators at the D-3 tailgate bleeder connectors were wide open and that no
additional ventilating pressure was available at these regulators. In addition,
the operator did not remove or adjust controls within the set-up rooms to affect
airflow distribution within the worked-out area.

A split of intake air, approximately 65,400 cfm, was
directed into the No. 1 entry of the D Seam Bleeders. This split of air was
intended to ventilate a pump that had been installed at the inby end of the
bleeder entries near the D-3 headgate bleeder connectors. The quantity of air
that ventilated the pump, approximately 15,000 cfm, was coursed directly into
the bleeder entries near the D-3 headgate entry bleeder connector regulators.
The remainder of this air was either directed intentionally into the bleeder
entries after ventilating other electrical installations or leaked through
ventilation controls into the bleeder entries. The large volume of leakage
reduced the methane concentration in the bleeder entry.

Bleeder System Ventilation
Controls

The adjacent D-2 longwall panel was sealed prior to
retreat mining of the D-3 panel. The seals in D-2 separated the D-2 panel gob
from the tailgate entry of the D-3 panel. As the D-3 panel was retreated, the
seals on the tailgate side inby the face became inaccessible.

The ventilation plan stipulated that seals were to be
completed in the headgate between the gob of the D-3 panel and the D-3
No. 2 headgate entry in each crosscut, as the retreating D-3 longwall face
passed the outby rib of the crosscut, except at the regulated opening at
MPL #4. Seals had been completed in Crosscuts 50 through 52 and across the
D-3 No. 1 entry between Crosscuts 53 and 54 in accordance with the approved
plan. The plan required that sample points be provided through the seals on
intervals of 1,000 feet as the longwall panel retreated. The locations were to
be monitored weekly. Because the D-3 panel had not yet retreated 1,000 feet, the
first sampling location had not been established.

Information gathered during the investigation revealed
that ventilation controls had been installed in the D-3 set-up entries. The
controls were constructed to facilitate the set-up of the D-3 longwall face and
were left in place to assist in controlling the face airflow during start-up. An
undercast was constructed in the intersection of the D-3 No. 1 headgate
entry and the inby set-up entry at Crosscut 53. Framed check curtains were
constructed in the crosscuts between the outby and inby set-up entries. A check
curtain was also hung across a one-crosscut long dogleg entry located inby
Crosscut 53. Testimony revealed the caved material was sufficient to
control face airflow prior to the accident, making these check curtains
unnecessary. The mixing chamber regulator was constructed under the top of the
D-3 No. 1 headgate entry undercast in Crosscut 53. A few blocks were
removed from the outby wall of the undercast to allow water entering the mine
from the D-3 panel gob to drain through Crosscut 53 and flow to the sump at
the back of the bleeder entries. The hole in the undercast was on the gob side
of the mixing chamber regulator.

Testimony indicated that the mine operator did not
travel into the setup room to make adjustments or to remove any controls after
the longwall commenced operation. The failure to make adjustments or to remove
controls affected the distribution of airflow in the gob. As installed, these
curtains would have inhibited airflow between the headgate side of the gob and
the inby set-up entry. These curtains, as well as the undercast, were not shown
in the approved ventilation plan drawings for retreat mining of the D-3 panel.
With these controls intact, airflow along the fringe of the headgate side of the
gob would have been further restricted, increasing the potential for methane to
accumulate in that portion of the gob.

Gob Ventilation Boreholes
and Degasification Systems

Vertical and horizontal gob degasification boreholes
were used to assist the mine ventilation system with the removal of methane from
the gob areas. The vertical degasification boreholes vented methane directly to
the surface. The horizontal degasification boreholes were connected to an
in-mine methane collection system that was exhausted to the surface. The
ventilation plan detailed information such as the design, operational
procedures, and criteria concerning the gob ventilation boreholes and
degasification system, and the horizontal degasification drilling and collection
system. The ventilation plan also permitted the removal of methane from sealed
gob areas through the in-mine methane collection system.

Vertical degasification boreholes were first used during
retreat of the D-1 panel. They assisted the mine ventilation system in the
removal of methane released from gob areas due to the fractures of the immediate
roof and floor caused by longwall extraction. The vertical degasification
boreholes were installed prior to the longwall extraction activities
intersecting them. Many of the boreholes were directionally drilled from the
same surface location. The ventilation plan permitted methane to free-flow from
the boreholes. The ventilation plan also permitted the use of exhaust pumps to
enhance methane removal. The minimum methane concentration in the borehole
exhaust permitted by the ventilation plan was 25 percent. Retreat mining in
the D-3 panel had not progressed sufficiently to intersect the D3-0 vertical
degasification borehole nearest the start-up location. Intersection with the
D3-0 vertical degasification borehole was expected within an additional
100 feet of retreat.

The horizontal degasification drilling and collection
system included long horizontal holes drilled from the mine entries into the
coal seam, roof and floor. Holes drilled into the roof strata are commonly
referred to as crossmeasure holes. The holes were connected to the in-mine
horizontal collection system that was routed to the surface. A centrifugal
blower, located on the surface, provided negative pressure to the system to
enhance methane drainage. The oxygen concentration within the collection system
was monitored. The ventilation plan required the surface degasification pumps to
automatically shut down when oxygen concentrations in the line exceeded
10 percent. The horizontal collection system was also connected through
seals to transport methane from the sealed D-1 and D-2 gobs.

Two horizontal degasification holes (HD3R1 and HD3R2)
were located in the roof coal of the D-3 panel outby the longwall face. Neither
had been intersected. Drilling was in progress on one of the holes. Additional
horizontal degasification holes were proposed. An existing inseam coal
exploration hole had been drilled across the D-3 and D-2 panels. Horizontal
degasification holes in both roof coal and floor coal were used near the end of
the D-2 panel.

Samples were collected at vertical degasification holes
located in the sealed areas during the week of July 23, 2000. The methane
concentration at these holes ranged from 21.61% to 66.25%. A sample collected
from the horizontal degasification system during the same week was 41.15%
methane.

Interior Gob
Ventilation

The primary airflow paths in a gob are generally those
with the least resistance. In a longwall gob, they generally are the middle
entries of the headgate and tailgate panels, the perimeter of the caved area,
the set-up rooms, the open area behind the longwall face and the recovery faces.
These primary airflow paths are critical to the successful operation of a
bleeder system. In highly gassy mines,methane
emanates from caved material and surrounding strata, or rubble zone, in
concentrations close to 100%. Dilution of the methane must occur. The methane
begins to dilute as it flows from the rubble into the primary airflow paths in
the gob. Further dilution occurs as the methane-air mixture moves into the
bleeder entries and out of the mine.

In a two entry system, the perimeter of the caved area
becomes the primary airflow path for the headgate and tailgate fringes. The
volume of airflow in these paths depends on many factors, such as the available
ventilating pressure, the tightness of the fall in the rubble zone, and the
resistance of the path to airflow. The resistance is affected by such factors as
roof falls, roof support, water, and ventilation controls. In gassy mines, the
use of a two entry system dictates that additional ventilation pressure, roof
support and pillar design be considered in maintaining adequate airflow through
primary airflow paths. In the D-3 panel, Can cribs (cylindrical steel roof
supports filled with low density concrete) were installed in the tailgate entry.
These Cans helped maintain the primary airflow path open in the tailgate side of
the gob. In the headgate, Can cribs were installed behind the seals but not in
the No. 1 entry. The primary airflow path in the headgate appears to have been
more restricted due to additional caving. This would have reduced the airflow
available to dilute methane as it was liberated from the rubble of the gob.

Generally, the typical primary airflow paths for a
longwall gob are not fully established until the longwall is advanced a distance
similar to its width. Until these paths are fully established, it is difficult
to maintain adequate distribution of the airflow in the gob. Frequent changes or
adjustments to headgate and tailgate regulators, ventilation controls adjacent
to the longwall face, and controls in the worked-out area are often necessary as
the initial falls occur. In the case of the D-3 panel, the majority of the air
ventilating the pillared area was confined to a relatively narrow path, as
compared to the width of the gob, flowing directly from the tailgate end of the
face to the tailgate bleeder connector. Additionally, typical internal airflow
paths were most likely not fully established in the D-3 panel as it was only
retreated approximately 250 feet. This would have increased the potential for
areas of varying restrictiveness to develop within the expanding pillared area.
Such conditions can create short circuits of the airflow within the pillared
area, leaving other areas isolated and inadequately ventilated. A means for
determining if adjustments were needed to compensate for such conditions to
maintain control of airflow through the pillared-area was not employed during
the operator's evaluations of the D-3 bleeder system. Full establishment of the
typical primary airflow paths wouldn't have been expected until after retreating
about 825 feet.

Ventilation Surveys and
Computer Simulations

A mine ventilation pressure-air quantity survey had been
conducted in the mine by MSHA in October, 1998. Additional information was
obtained during the investigation from other sources such as: the required mine
record books; the interviews and discussions with MSHA enforcement personnel and
the mine operator; and the ventilation simulations completed by the mine
operator. This information was used to develop a model of the mine ventilation
system prior to the events of July 31.The model demonstrates a number of
weaknesses in the mine's ventilation system.

The airway paths through the gob become increasingly
resistant as retreat mining progresses. These increases in resistance occur over
the life of the longwall panel. Sufficient additional ventilating pressure
differential is necessary to compensate for these increases in resistance if the
same airflow is to be provided for ventilation of the worked-out area. If
changes in contaminant liberation require additional airflow, even greater
ventilating pressure is necessary. The design of the system was such that
airflow passing through the worked-out area of the D-3 longwall panel was
largely controlled through adjustment of regulators located in the tailgate
bleeder connectors. The pressure differential that exists across a regulator is
the reserve ventilating pressure at that point in the system. This reserve
pressure is used to sustain, or increase, the ventilation through the worked-out
area. The magnitude of that reserve pressure compared to the ventilating
pressure applied to ventilate the worked-out area is a measure of the available
capacity. Generally, the opening in the regulator is increased to transfer the
reserve pressure. Statements revealed that the regulators in the tailgate
bleeder connectors were fully opened. The other means to increase the system's
ventilating capacity was through changes in operation of the main mine fan. Mine
records indicated that the main mine fan was producing approximately
850,000 cfm at 9.7 inches of water. The fan blades were reportedly set
at the 19.5 degree blade position. Mine management indicated that the motor
for the fan was operating near its capacity and was monitoring motor amperage.
This effectively limited further increases in ventilating pressure or airflow
for the bleeder system. Therefore, the bleeder system had limited reserve
capacity.

Airflow from the bleeder split ventilating the pillared
portion of the worked-out area consistently contained methane in excess of 2.0
percent after July 29, 2000. Airflow from the regulator at the pump room and
from MPL #5 and MPL#6 diluted the methane downwind of MPL #8. However, methane
concentrations in the bleeder airflow continued to increase. These changes in
conditions should have prompted an investigation to ensure that ventilation was
adequate. Improved distribution and/or additional airflow through the pillared
worked-out area was needed to dilute and remove the methane being liberated.
However, as a result of the system's configuration and because the regulators
near MPL #7 and MPL #8 were fully open, no additional capacity was readily
available.

Computer simulations were developed to evaluate possible
conditions in the mine after the first and third explosions. These simulations
are based on the results of testimony taken during the investigation, on fan
pressure recording information, and the results obtained from the AMS data.
These simulations show that ventilation controls inby the longwall face in the
headgate entries and in the D Seam Bleeders were likely to have been damaged
after the first explosion. They also show that the effectiveness of the
ventilation system for the D-3 longwall would have diminished significantly
after the first explosion. This would have decreased the airflow within the
primary airflow paths along the fringes of the gob and would have increased the
volume of explosive gas along those fringes of the gob. The small magnitude of
the second explosion did not materially affect the ventilation system.
Therefore, no simulations were developed. The computer simulations also indicate
that the third explosion probably caused additional damage to ventilation
controls in the mine. They also show that the effectiveness of the ventilation
system for the D-3 longwall would have further diminished. The fourth explosion
probably caused additional damage to ventilation controls in the mine.

Methane Liberation

Excluding the degasification systems, and as determined
through analyses of vacuum bottle air samples and air quantity measurements
taken during an MSHA inspection on July 6, 2000, methane liberation
was 2,832,000 cubic feet per day (cfd). The mine's measured total return
airflow on that date was 732,000 cfm. The D-2 panel was not yet sealed and
retreat mining in the D-3 panel had not begun as of July 6, 2000. Mine
officials collected air samples for analysis at specific locations during
regular weekly examinations. The results of the analyses of these samples and
the air measurements taken during these weekly examinations provide information
about the change in methane liberation from the bleeder system. Information
collected on July 18 and 19, 2000, indicated that methane liberation
from the bleeder system (at MPL B1, MPL B2, and MPL B3) was
2,519,000 cfd and total mine methane liberation in the main return entries
was 3,235,000 cfd (an increase of 403,000 cfd from July 6 to
July 19, 2000). The D-2 panel was sealed at that time and retreat
mining in D-3 panel had just begun. Air samples collected on July 25 and
26, 2000, indicated methane liberation from the bleeder system (at
MPL B1, MPL B2, and MPL B3) had increased to 6,338,000 cfd
(an increase of 3,819,000 cfd from July 19 to
July 26, 2000). By the night of July 31, 2000, methane liberation from
the D-3 bleeder system had increased to over 7 million cfd.

Cut-outs on the tailgate and headgate routinely caused
relief of stresses in the strata. The conditions on the tailgate resulted in
sudden significant quantities of methane being released. The methane releases
regularly caused production to cease because of resulting elevated methane
concentrations on the face. Additionally, methane feeders were encountered at
other locations on the face that resulted in production delays. Production
resumed as the methane release decreased.

The methane concentration in the airflow exiting from
the D-1 Tailgate No. 1 entry at MPL B1 was continuously monitored and
recorded by the AMS. The system also monitored and recorded the methane
concentration in the D-3 tailgate bleeder connectors (MPL #7 and
MPL #8). Figure 3 (see Appendix F) shows the methane concentrations
recorded by the AMS at MPL #5, MPL #6, MPL #7, MPL #8, and
MPL B1. Fluctuations in methane concentrations at MPL B1 coincided
with those at the tailgate bleeder connectors. However, during the last few days
prior to the accident, the difference between methane concentrations at the
tailgate bleeder connectors and those at MPL B1 widened, indicating that gob
airflow constituted a smaller percentage of the airflow at MPL B1. Increasingly
restrictive airflow paths developed within the pillared area as the longwall
retreated, and resulted in decreased airflow through the bleeder connectors. The
methane concentrations at the two headgate bleeder connectors were relatively
stable during the entire time the D-3 panel retreated.

Methane liberation from the D-3 panel was significantly
influenced by production rates as well as the increase in size of the gob area.
Figure 4 (see Appendix F) shows the recorded methane concentrations at the
tailgate bleeder connectors (MPL #7 and MPL #8) and the approximate
number of passes mined each shift. Production reports were used to determine the
approximate number of passes mined each shift. The methane liberated from the
D-3 panel increased during production. Conversely, during the idle shift
following the afternoon production shift and during idle periods on the
production shifts, the methane concentration in the bleeder airflow decreased.
It appears the production rate and methane liberation rate had somewhat
stabilized prior to July 29, 2000. Beginning on July 29, the total
number of passes mined each day increased. Also, on July 29, the methane
liberation trend changed. The increase in methane liberation, combined with a
decrease in airflow through the pillared area during the days prior to the
accident, increased the methane concentrations in the gob at the time of the
accident.

Hydrocarbons

Underground coal extraction at the mine results in the
release of liquid hydrocarbons from the surrounding strata. Procedures to
alleviate the health and safety concerns associated with the presence of these
hydrocarbons were addressed in the longwall hydrocarbon procedure portion of the
ventilation plan submitted by Plateau Mining Corporation. Personal protection,
including jackets, gloves, and respirators, was required. Also, since the
hydrocarbons are similar to diesel fuel, longwall personnel were required to
review the Material Safety Data Sheet for diesel fuel. Hydrocarbons were to be
directed away from work areas and equipment.

The ventilation plan also required that hydrocarbons be
cleaned off equipment twice per shift. Where visible on the face, they were to
be diluted with water. Ventilation quantities were to be increased 10% above
approved quantities when hydrocarbons were present. A number of additional
precautions were to be taken when hydrocarbons were present in the vicinity of
welding/cutting activities.

The occurrence of hydrocarbons was not uniform
throughout the mine. However, interviews of knowledgeable miners revealed that
hydrocarbons were present on the longwall face of the D-3 longwall prior to and
on July 31, 2000. As liquid hydrocarbons entered the mine, they dripped or
flowed to the floor. The slope of the active D-3 section caused liquid
hydrocarbons and water from the face area to flow inby to a sump in the bleeder
entries. From this point, the liquid hydrocarbons and water were removed from
the mine. Although information was not available concerning quantities at the
time of the accident, about 1,200 gallons per day were being pumped outside at
various times during 1998.

Data Chem Laboratories evaluated a sample of the liquid
hydrocarbons and reported the results of their findings in a letter dated May 4,
1998. Their analysis noted that the composition of the sample was roughly
equivalent to a mixture of 15% automotive gasoline, 35% kerosene (diesel fuel),
and 50% light lubricating oil (motor oil). The sample contained measurable
quantities of approximately 34 individual compounds. The volatile portion
reportedly included isobutane, butane, pentanes, and hexanes in significant
quantities. Toluene, benzene, and xylenes were also found.

Gases from the liquid hydrocarbons were released into
the mine atmosphere in two ways as the hydrocarbons entered the workings.
Primarily these gases were liberated as they entered the workings with the
liquid hydrocarbons. This portion of the hydrocarbon gases was noticeably
evident by the strong associated odors, not only throughout the section but
occasionally also to the surface areas of the mine. The second manner of entry
occurred as the volatile portion of the liquid entered the mine atmosphere as
vapor. This process is exacerbated as the temperature increases, especially if
the flash point of the liquid is exceeded.

If the flash point of the liquid hydrocarbons is
exceeded, ignitable vapors are released. The flash point is the temperature at
which a liquid begins to give off ignitable vapors. The flash point of
hydrocarbons taken from the Willow Creek Mine was established to be
approximately 97� F during an analysis conducted by Chevron in 1998. Although
ignitable hydrocarbon vapors can occur at temperatures of 97� F or higher, the
ignition temperature for those vapors is expected to be approximately 500� F.
MSHA's Approval and Certification Center (ACC) received a sample of hydrocarbons
from the mine. The sample was not fresh and a significant portion of the
volatile content had previously been exhausted, causing any flash point and
ignition temperature determinations to be inconclusive in relation to the
hydrocarbons on the day of the accident. However, upon igniting a thin layer of
the hydrocarbons, the flame reached nearly two feet in height and produced
copious amounts of smoke.

In 1998 Data Chem Laboratories established the explosive
range of the hydrocarbon gases to be between 1.03% and 5.36%. Methane, also a
hydrocarbon, has a lower explosive limit of 5%. However, the combination of
these gases would cause the lower explosive limit of the mixture to be less than
5.0%. Significant volumes of the hydrocarbon gases would not be expected to have
been present, if adequate ventilation was maintained. Due to the volume of
methane being liberated, methane was the more significant fuel source in the D-3
gob for the explosions of July 31 and August 1, 2000.

The first explosion ignited methane and likely ignited
hydrocarbon vapors, resulting in fire around and behind the headgate shields.
Parts of the fire remained inaccessible. Water was ineffective in fighting the
accessible portion of the fire. An adequate supply of a suitable
fire-extinguishing agent was not available. The fire continued to spread through
inaccessible areas of the D-3 gob and provided an ignition source for subsequent
explosions. Liquid hydrocarbons were eventually ignited.

Examinations

Mine examinations were conducted by various certified
miners pursuant to the requirements of 30 CFR 75.360 through 75.364. Those
miners included both salaried and hourly Willow Creek employees as well as
contractor employees permanently assigned to the Willow Creek Mine. In general,
section foremen would conduct preshift examinations and various outby personnel
would conduct portions of the weekly examination. There were no miners
designated solely as mine examiners.

The mine operated two, 10-hour longwall production
shifts which began at 6:45 a.m. and 3:45 p.m., respectively. A maintenance shift
began at 10:00 p.m. Preshift examinations were performed based upon three,
8-hour time periods not associated with the start of the production or
maintenance shifts. For preshift examination purposes, the examinations were
conducted within three hours of the following designated times: 2:30 a.m.; 10:30
a.m.; and 6:30 p.m.

Among the D-3 longwall shift foremen interviewed during
the investigative process, there was confusion regarding the location of the air
measurement required by 30 CFR 75.360(c)(2). That measurement, which was
required to be taken immediately outby the longwall face to determine the volume
of air reaching the longwall face, was often taken either outby the last open
crosscut in the No. 2 headgate intake entry or in the last open crosscut. The
air volume at those locations would have included airflow reaching the face, air
exiting in the belt entry, and, in the case of the reading taken in the No. 2
entry, air traveling inby toward the D-3 setup rooms and the bleeder entries.
The reviewed records and testimony indicated that some of the air measurements
were not taken in proper locations. The examiners interviewed were not fully
aware of the requirements of the regulation regarding the proper location of
this required measurement.

Section 75.364(c)(1), 30 CFR, requires the examiner to
determine the volume of air entering the main intakes and in each intake split .
The air volume measurements were not conducted in the air course ventilating the
idle belt of the D Seam Bleeders. This split was isolated by permanent
ventilation controls and was functioning as a distinct intake air course before
being regulated into the main return. The split was approximately 1,600 feet in
length. The investigation revealed that the air volume was not determined in the
belt air course during the weekly examinations and was not recorded in the
record book.

Weekly examinations were routinely conducted during a
two-day period, primarily during the day shift on Tuesdays and Wednesdays. Due
to rotating shifts and varying work schedules, it was rare for the same miner to
conduct any portion of the weekly examination for more than two consecutive
weeks. This caused a lack of continuity in making a determination of changing
conditions along the traveled routes. Several of the mine examiners voiced this
concern to mine management prior to the explosions on July 31 - August 1.
Management believed that regular examinations by the same miners could result in
complacency. During testimony, some mine examiners could not explain
discrepancies in the examination records.

Weekly examiners were provided a map and a listing of
the designated locations requiring measurements for the weekly examination. The
examiners traveled to those locations, took measurements, and recorded the
information in the appropriate record book. However, when questioned during the
interviews, the examiner who conducted the most recent weekly examination was
unable to identify many of the locations where the recorded measurements were
taken. Most of those locations were in the D-3 bleeder system. In addition, when
presented with earlier conflicting measurements, another mine official was
unable to provide an explanation.

The mine manager was responsible for countersigning and
reviewing the examination records. It was his responsibility to make
determinations as to the efficiency and adequacy of the ventilation system based
upon his review of the records. The mine manager did not routinely correlate the
measurements of the weekly examinations with previous examination results, or
their locations in the mine, to determine whether any abnormalities were
developing. The focus was on making sure that the examinations and records were
completed. Many of these measurements were related to the ventilation of the D-3
longwall bleeder system.

Mine management implemented a mine examination system
whereby the individual examiners had little responsibility for, or authority to
act on, the results of the weekly examinations. The system provided for a
management official, primarily the mine manager, to review, countersign, and
evaluate the results of the weekly examinations. The requirements of the
regulations corresponding to the weekly examinations were fulfilled with respect
to the physical measurements and record keeping. However, the results were not
used to identify trends or changes developing within the system.

Origin, Flame and Forces

On July 31, 2000, the afternoon shift began at 3:45
p.m., as the working crews traveled underground. The shift was to continue until
1:45 a.m. on August 1. Mining and related activities continued normally
throughout the shift until the time of the first explosion.

First Explosion

Most likely, a roof fall in the headgate fringe area of
the gob, between the longwall face and the longwall set-up rooms, ignited a
small pocket of methane and other gaseous hydrocarbons. The flame traveled inby
to a methane accumulation in the back of the gob near the longwall set-up rooms.
The ignition of this methane resulted in the first explosion at 11:48 p.m. on
July 31. Flame from the initial ignition also traveled toward the longwall face
and ignited methane feeders and, eventually, the vapors from the liquid
hydrocarbons.

Elevated CO readings occurred in the bleeder entries and
in the D-3 No. 1 headgate entry. The monitors near the headgate bleeder
connector regulators experienced a communication failure. Data from the CO
monitors near the tailgate regulators at the bleeder entries indicated
concentrations in excess of 50 ppm shortly after the explosion. Data from the CO
monitor at MPL B2 showed that the concentrations began to increase approximately
21 minutes after the explosion and, within an additional two minutes, the
readings were in excess of 50 ppm. Data from the CO monitors in the No. 1
headgate entry outby the face revealed that elevated concentrations of CO
occurred at the monitor locations near the longwall face. Data from each outby
sensor also showed elevated concentrations. This is consistent with the
incomplete combustion of fuel during an explosion.

The miners working on the longwall section did not
report seeing any flame or feeling any heat from the first explosion. The miners
on the longwall face felt the pressure of the explosion followed by dusty
conditions, but initially thought it occurred as a result of a massive roof fall
in the gob. The reported effects of the explosion across the longwall face are
consistent with pressures of less than 0.5 pounds per square inch (psi). The
miners on the longwall face near the headgate immediately observed fire on the
floor near Shield 8. The miners at Crosscut 48 of the headgate experienced a
pressure wave that was propagating from the No. 2 entry. The reported effects of
the explosion in this area are consistent with pressures of approximately 1 psi.
The reported effects in the No. 2 entry are consistent with a pressure wave of
about 2 psi. This pressure would have been sufficient to damage the regulator in
the No. 1 entry inby Crosscut 51. Life-threatening injuries did not occur as a
result of this first explosion.

The first explosion occurred in the No. 1 headgate entry
of the D-3 section near the longwall set-up rooms. The explosion probably
generated pressures of approximately 5 psi near the origin. However,
obstructions prevented the full thrust of the explosion from propagating outby
in the No. 1 entry. As little as 50 cubic feet of methane, diluted to about
6.5%, would be capable of generating this limited pressure. The 5 psi force
would be sufficient to damage the undercast and regulator in the mixing chamber.
The force exiting the headgate into the bleeder entries was approximately 3 psi.
This pressure would be sufficient to severely damage both the headgate
regulators and the nearby controls in the bleeder entries. These regulators were
both nearly closed prior to the explosion. The force reaching the tailgate
bleeder regulators was probably 2 psi. Both regulators were significantly open.
This pressure may have been sufficient to damage both of these regulators.

The forces generated during an explosion can increase,
decrease, or remain constant throughout an explosion zone, depending on the
amount of fuel that continues to be available. In the absence of an underground
investigation, firsthand facts pertaining to the propagation of flames and the
resulting generation of explosion forces could not be confirmed by the
investigators. However, it is reasonable to believe that limited forces could be
maintained for significant distances. For example, pressures of less than 1 psi
could have caused doors in outby areas of the bleeder entries to be forced into
an open position.

Based on the expected generation of forces and
statements from the witnesses, it is likely that the first explosion compromised
the mixing chamber regulator, the undercast in the gob, and the regulators
located in the headgate entries inby the face. Primary explosion forces
propagated into the bleeder entries and outby in the No. 2 headgate entry toward
the face. Because an underground investigation was not possible, the degree of
involvement of coal dust, if any, and damage to the bleeder entries could not be
ascertained. No miners traveled the bleeder entries after the explosion.
However, it is believed that ventilation controls in the bleeder entries, in
addition to those mentioned above, were significantly damaged or otherwise
compromised due to the force of the first explosion.

Immediately after the first explosion, fire was observed
in the vicinity of Shield 8 by one of the shearer operators. The liquid
hydrocarbons were subjected to temperatures which exceeded both their flash
point and their ignition temperature during the explosion. The fire was able to
spread along the surface of the liquid hydrocarbons and along any available
methane floor feeders. The fire continued to burn at least in the vicinity of
Shields 3 to 8. Fire fighting activities were on-going with the use of 10-pound
fire extinguishers and water. This effort had little effect on the overall fire
due to the fact that much of the fire occurred in inaccessible areas behind the
shields.

Second Explosion

The ventilation controls, compromised in the first
explosion, resulted in a disruption of the ventilation of the gob. The area and
volume of methane, between the rubble zone and the longwall face, increased.
Shortly before the second explosion, fire was increasing in intensity, rolling
behind the shields, indicating that additional methane accumulations were
becoming involved. The second explosion occurred as a methane accumulation was
ignited by the fire at approximately 11:55 p.m. on July 31. Primary explosion
forces, although limited, propagated along the face toward the headgate and
outby in the No. 1 entry.

The second explosion was not discernable on the fan
chart and was not recorded by the monitoring system. Evidence indicates that
forces generated during the second explosion were of a lower overall magnitude
than those of the first explosion. However, injuries were more significant due
to the proximity of miners to the origin of the second explosion. It is likely
that fatal injuries occurred to Nielsen as a result of the second explosion.
High levels of CO were present in and around the longwall face after this
explosion.

Third Explosion

The area and volume of methane along the fringes of the
gob continued to increase. Turbulence from the second explosion most likely
caused high concentrations of methane from the fringes of the gob to mix with
air. This accumulation along the fringes of the gob near the set-up rooms, was
most likely ignited at approximately 11:56 p.m. The period of time between the
second and third explosions was probably limited to less than one minute.
Considering the burning rate of methane, it is conceivable that the third
explosion was a continuation of the second explosion and not a separate event.
The primary forces from this explosion propagated inby in the No. 1 entry and
outby along the headgate fringe of the gob. Forces continued outby through
Crosscut 53 and into the No. 2 entry. Forces also traveled into the bleeder
entries. The fan pressure chart showed a spike in the pressure following this
explosion. A sudden decrease in fan operating pressure resulted. It is likely
that fatal injuries occurred to Stansfield as a result of the third explosion.

Considering all pertinent information, it is likely that
the third explosion was the most powerful explosion. The miners working on the
longwall section did not report seeing any flame or feeling any heat from the
third explosion. The miners on the longwall face felt the pressure of the
explosion but indicated that it was not as strong as the second explosion. The
reported effects of the explosion across the longwall face are consistent with
pressures of less than 1 psi. The miners near the mantrip in the headgate
experienced a pressure wave that propagated outby in the No. 2 entry. The
reported effects of the explosion in this area are consistent with pressures of
approximately 2 psi. As with the first explosion, obstructions prevented the
full thrust of the explosion from propagating outby along the headgate fringe of
the gob.

Fourth Explosion

A pressure spike on the fan operating chart and the
monitoring system indicated that a fourth explosion occurred at approximately
12:17 a.m. on August 1, 2000. No miners underground recalled the fourth
explosion.

Potential Ignition Sources

A determination of the potential ignition sources is
based on several factors. These factors typically include:

identification of the available fuels;

ignition temperatures and energies of the
available fuels;

visual observations;

statements from witnesses and other persons
with knowledge of the circumstances surrounding the explosion;

location of all ignition sources near the
suspected origin;

the activities that were being conducted at
the time of the explosion;

the location of all miners in the vicinity of
the ignition; and

subsequent evaluations of ignition sources
within the explosion zone.

The available fuels considered for the first explosion
are methane, coal dust, and hydrocarbons. Methane was liberated from the mine
and it did occur in significant quantities in the area of the mine where the
series of explosions occurred. The ignition temperature for methane is
approximately 1000F. The energy necessary to ignite methane is approximately 0.3
millijoules. Methane is ignitable at concentrations between 5% and 15%. Coal
dust layers can be ignited at temperatures as low as 320F and coal dust clouds
can be ignited at temperatures as low as 824F. The energy necessary to ignite
bituminous coal dust is about 60 millijoules. Layers of coal dust averaging only
0.005 inch thick can propagate an explosion, if suspended. Hydrocarbons from the
Willow Creek Mine have a flash point of approximately 97F. This is the
temperature at which the hydrocarbons give off ignitable vapors. However, the
ignition temperature for those vapors is approximately 500F. Ignition energies
are not well established for these particular hydrocarbons.

The fuel for the first explosion was most likely
methane. Coal dust would not have been in suspension to the degree necessary for
explosion propagation. Hydrocarbon vapors alone would not have been present in
the volumes necessary to support a continuing explosion flame. However, the
ignition of methane eventually resulted in prolonged burning of sporadic liquid
hydrocarbon accumulations in the headgate fringe of the gob of the D-3 panel.
This burning provided a continuing source of ignition for subsequent explosions
propagating from the gob area.

Viable potential ignition sources must be capable of
exceeding either the temperature or energy requirements of the fuel. Visual
observations were not possible in this case because the mine was sealed and an
underground investigation could not be conducted. However, the existence of
potential ignition sources has been verified through the statements by witnesses
and other persons with knowledge of the circumstances surrounding the initial
explosion.

Witness statements and other information obtained during
the investigation were used to identify an area in which the first explosion
originated. This area includes the longwall face, the headgate entries inby the
face, the fringe of the gob on the headgate side from behind the shields to the
set up rooms, the headgate side of the set up rooms and the bleeder entries. All
ignition sources within this area were considered in establishing the potential
ignition sources for the first explosion.

The locations of miners underground and the activities
that were being conducted are important in identifying the potential ignition
sources. Very few ignitions have occurred over the past twenty years that did
not directly involve the actions of those working underground at the time of the
explosion. However, those extraneous sources were also considered and will be
discussed in this section of the report.

Although equipment and other ignition sources are
typically evaluated after an explosion, none were removed because an underground
investigation was not possible. Therefore, laboratory testing was not used as a
tool to eliminate or identify any particular source of ignition.

All of the available information concerning possible
ignition sources for the first explosion was examined. The following ignition
sources were considered:

roof fall inby face along the headgate fringe of the
gob;

falling rock impacting on seams on Can cribs;

tensile failure of cable bolts or trusses;

operation of pumps in bleeder entries;

breaking of wire rope tied between Shield 1 and the
shearer;

operation of face conveyor;

the operation to advance the shields;

operation of shearer;

shearer cutting roof or rib bolts;

cutting/welding operations;

material passing through crusher;

smoking;

spontaneous combustion;

lightning, and;

compression of air due to a large roof fall.

Roof falls occurred in the gob of the D-3 panel.
Sandstone formations contain varied degrees of quartz. Quartz, which is a
crystalline structure, is known to exhibit a "piezoelectric effect".
Piezoelectricity is the development of electrical charges on the surface of the
crystal. Sparking occurs when this electrical charge is dissipated. This
sparking can provide the energy needed to ignite flammable gases and vapors. A
roof fall is the most likely potential ignition source for the explosion.

The Cans used for roof support reportedly were
constructed with welded seams. The mine operator indicated that roof falls
impacting on the seams could generate sparks and that tape on the seams would
minimize the hazard. However, the operator declined to provide information on
tests conducted on these roof supports. Preliminary and informal tests had been
performed by the National Institute of Occupational Safety and Health, formerly
the Bureau of Mines, which indicated that sparks generated by rocks impacting
the Cans were not likely to ignite methane. However, because formal testing was
not conducted, conclusive results of testing on the incendive nature of these
Cans was not available to the investigation team. Therefore, roof falls against
exposed seams remains as a potential ignition source.

Recent testing of cable bolts has shown that their
failure did not ignite methane. However, the tensile failure of cable bolts or
trusses is theoretically capable of igniting methane, under certain conditions.
Depending on their location and on the location of methane accumulations within
the explosive range, tensile failures of either cable bolts or trusses may be a
potential source of ignition for the explosion.

Pumps and their associated control boxes, located in the
intake split adjacent to the bleeder entries, could have ignited methane. An
evaluation of pumping equipment and an investigation of the surrounding area was
not possible. An examination of the bleeder entries near the pumping equipment
was conducted earlier in the shift on the day of the explosion. The pump was not
operating at the time. Water had accumulated near the pump to within
approximately 3 feet from the roof. It is possible that additional water inflow
or a roof fall in the area of the water occurred which caused an interruption in
the ventilation and allowed methane to accumulate. However, this is not likely
because of the relatively short time period between the examination and the time
of the explosion. Additionally, it is unlikely that an explosion initiating near
the pump or its associated controls would result in an almost instantaneous fire
at the longwall face. The pumping equipment is not considered as a potential
source of the explosion.

Statements were made by witnesses that Shield 1 was not
being advanced at the time of the first explosion. Therefore, the wire rope used
in advancing Shield 1, immediately prior to the accident, had not experienced a
tensile failure. It is not considered as a potential source for the
explosion.

The operation of the face conveyor was considered as a
potential ignition source. Although, methane can accumulate under the panline of
face conveyors, miners were in the proximity of the panline and did not report
methane or flames. Also, testimony indicated that the face conveyor was not
operating immediately prior to the explosion. The operation of the face conveyor
is not considered as a potential source of the explosion.

Frictional heating between the shields and the roof or
roof supports would not be capable of generating the necessary temperatures for
hydrocarbon or methane ignition. However, there could be sufficient energy
generated during the process to ignite these gases. It is unlikely that
ignitable gas concentrations existed at this location because of the volume of
airflow in this area. Additionally, information was obtained during interviews
to indicate that shields were not being moved at the time of the explosion.
Therefore, the operation to advance the shields is not considered as a potential
ignition source.

Although the operation of the shearer could ignite
methane, the shearer was not cutting at the time of the explosion. Miners were
in the immediate proximity of the shearer and did not state that methane was
ignited at this location. The volume of airflow in the area was sufficient to
prevent any accumulations of ignitable methane concentrations. Additionally, the
recorded amperage used by the shearer had dropped to insignificant levels about
four minutes prior to the event, further eliminating the shearer as a potential
source for the explosion.

Although the cutting of roof or rib bolts by the shearer
could ignite methane, it was not cutting at the time of the explosion.
Therefore, the cutting of roof and rib bolts was not considered a potential
ignition source.

There was no indication that cutting/welding operations
were ongoing at the time of the explosion. Therefore, cutting/welding operations
were not considered a potential ignition source.

Material passing through the crusher portion of the
stageloader can create sufficient energy to ignite gas. Miners were working in
the area and they did not report anything unusual in this area. The ignition of
methane accumulations in the crusher portion of the stageloader would have
caused flames to travel into the face area. Miners on the face did not report
seeing flames at or near the stageloader prior to the first explosion.
Therefore, material passing through the crusher is not considered a potential
ignition source.

Investigators found no evidence to indicate that smoking
was the ignition source. Therefore, smoking is not considered a potential
ignition source.

There was no history of the occurrence of spontaneous
combustion in the mine. The AMS did not record any elevated levels of carbon
monoxide prior to the explosion. Therefore, spontaneous combustion is not
considered a potential ignition source.

There were no reports of lightning at the time of the
explosion. The report obtained from Global Atmospherics, Inc., shows that there
were no lightning strikes in the area at or near the time of the explosion.
Therefore, lightning is not considered a potential ignition source.

Heating of the atmosphere from the compression of air
can only occur under extreme circumstances. A roof fall of a massive area would
be necessary to cause such a condition. Mine maps revealed that there was not an
open area in the D-3 panel large enough for this condition to occur. Miners on
the face would have suffered fatal injuries associated with the resulting force
of such a roof fall. However, the miners on the face did not experience injuries
to this extent. Therefore, compression of air is not considered a potential
ignition source.

The most likely ignition source for the first explosion
is a roof fall. Two other potential ignition sources are roof falls against
exposed seams of Can roof supports and the tensile failure of cable bolts. All
three potential ignition sources were located in the headgate fringe area of the
gob.

CONCLUSION

The bleeder ventilation system did not adequately
control and distribute the air passing through the worked-out area of the D-3
Panel. The system did not continuously dilute and move methane-air mixtures and
other gases, dusts, and fumes from the worked-out area away from active workings
and into a return air course or to the surface of the mine.

Several factors adversely impacted the bleeder
ventilation system prior to the accident. An increase of coal production on the
longwall face and an expanding gob resulted in greater methane liberation into
the gob. This increase in liberation was accompanied by a decrease in the total
quantity of airflow within the gob. Although vertical degasification boreholes
were drilled for the panel, the first vertical degasification borehole had not
yet been encountered. In addition, the mine ventilation and bleeder
system had limited reserve capacity and the availability of ventilation pressure
and air quantity was further reduced by the intake air split adjacent to the D
Seam Bleeders. The distribution of airflow in the gob was affected by the lack
of fully established internal airflow paths as well as by ventilation controls,
such as check curtains and an undercast, that were left intact in the
worked-out area.

Most likely, a roof fall in the headgate fringe area of
the gob, between the longwall face and the longwall set-up rooms, ignited a
small pocket of methane and other gaseous hydrocarbons. The flame traveled inby
to a methane accumulation in the back of the gob near the longwall set-up rooms.
This resulted in an explosion and fire at 11:48 pm on July 31, 2000. An
interruption of ventilation of the D-3 gob, caused by the explosion, prevented
methane removal from the gob. Eventually, liquid hydrocarbons became involved in
the fire. Fatal injuries did not occur as a result of the first explosion.

After the first explosion, personnel remained on the D-3
longwall section to extinguish a fire near the base of the shields on the
headgate side of the longwall face. Conditions worsened in the face area just
prior to the second explosion. The fire, resulting from the first explosion,
ignited subsequent explosions. Fatal injuries likely occurred as a result of the
second and third explosions.

Approved:

_____________________________

Marvin W. Nichols, Jr.

Administrator

ENFORCEMENT
ACTIONS

30
CFR 75.334(b)(1) During pillar
recovery a bleeder system shall be used to control the air passing through the
area and to continuously dilute and move methane-air mixtures and other gases,
dusts, and fumes from the worked-out area away from active workings and into a
return air course or to the surface of the mine.

Violation: During
pillar recovery of the D-3 Longwall Panel, the bleeder system being used did not
control and distribute air passing through the worked-out area in
a manner which continuously diluted and moved methane-air mixtures and other
gases, dusts, and fumes from the worked-out area away from active workings and
into a return air course or to the surface of the mine.

The following factors impaired the bleeder
system's effectiveness at controlling and diluting the air passing through the
worked-out area: a limited mine ventilating potential; the configuration and
distribution of airflow in the bleeder system and worked-out area; and temporary
controls installed within the worked-out area which restricted airflow through
the pillared area. As production increased and the pillared area expanded,
methane liberation increased and airflow paths changed within the worked-out
area. These changing conditions resulted in reduced airflow and elevated methane
concentrations within the worked-out area at locations containing potential
ignition sources and within close proximity to the active longwall
face.

On July 31, 2000, an explosive concentration of
methane-air mixtures and/or other gases, dusts, and fumes had accumulated in the
worked-out area, within 250 feet of the working D-3 Longwall face. At
approximately 11:48 p.m., a portion of the atmosphere in the worked-out area was
ignited, resulting in an explosion which injured a miner working on the D-3
Longwall Section. The initial explosion created conditions which resulted in
additional explosions within or near the worked-out area. The subsequent
explosions resulted in fatal injuries to two miners located on the D-3 Longwall
Section.

30
CFR 75.370(a)(1):The operator
shall develop and follow a ventilation plan approved by the district manager.
The plan shall be designed to control methane and respirable dust and shall be
suitable to the conditions and mining system at the mine. The ventilation plan
shall consist of two parts, the plan content as prescribed in §75.371 and the
ventilation map with information as prescribed in §75.372. Only that portion of
the map which contains information required under §75.371 will be subject to
approval by the district manager.

Violation:
The approved mine ventilation plan was not being complied with in that
ventilation devices used to control air movement through the D-3 worked-out area
were left in tact after retreat mining commenced at locations not shown on the
supplement to the mine ventilation plan titled, "D-3 LONGWALL START-UP HEAD TO
TAIL AND BLEEDER VENTILATION WITH TAIL GATE INTAKE," approved July 7, 2000.
Information obtained during the investigation of a fatal mine fire and explosion
accident which occurred on July 31, 2000, established that the mine operator
installed framed curtains across four of the six bleeder connectors at the inby
end of the D-3 Longwall pillared area. Also, an overcast and check curtain were
installed in the bleeder connector nearest the headgate side of the worked-out
area, leaving one unobstructed bleeder connector which was located on the
tailgate side of the worked-out area. However, the approved plan supplement did
not show controls at these locations. These controls inhibited airflow on the
headgate side of the worked-out area where the initial explosion and subsequent
fire occurred on July 31, 2000.